using System;

using System.Collections.Generic;

using System.Linq;

​

namespace Example

{

    interface IDeviceContext

    {

        void StartTexture();

        void EndTexture();

        void Paint(string o);

    }

​

    class DeviceContext : IDeviceContext

    {

        public void StartTexture()

        {

            Console.WriteLine("Starting texture on device context.");

        }

​

        public void EndTexture()

        {

            Console.WriteLine("Ending texture on device context.");

        }

​

        public void Paint(string s) 

        {

            Console.WriteLine("Drawing {0}", s);

        }

    }

​

    abstract class RenderObject

    {

        public string Name { get; set; }

​

        public List<RenderObject> Children { get; private set; } 

​

        protected readonly IDeviceContext _context;

​

        public RenderObject(IDeviceContext context)

        {

            _context = context;

            Children = new List<RenderObject>();

        }

​

        public void Render()

        {

            this.RenderInternal();

            foreach (var o in Children) o.Render();

        }

​

        protected abstract void RenderInternal();

    }

​

    class ImageRenderObject : RenderObject

    {

        public string ImageFile { get; set; }

​

        public ImageRenderObject(IDeviceContext context) : base(context) {}

​

        protected override void RenderInternal()

        {

            Console.WriteLine("ImageRenderObject '{0}' is rendering an image of {1}", this.Name, this.ImageFile);

        }

    }

​

    class TexturedRenderObject : RenderObject

    {

        public TexturedRenderObject(IDeviceContext context) : base(context) {}

​

        protected override void RenderInternal ()

        {

            _context.StartTexture();

            Console.WriteLine("TexturedRenderObject is rendering {0}", this.Name);

            _context.EndTexture();

        }

    }

​

    //Not really needed, but you can do this if you want to

    class CullingBird : ImageRenderObject

    {

        public CullingBird(IDeviceContext context) : base(context) 

        {

            this.ImageFile = "CullingBird.png";

        }

​

        protected override void RenderInternal()

        {

            Console.WriteLine("ImageRenderObject '{0}' is rendering an image of {1}", this.Name, this.ImageFile);

        }

    }

​

    //Not really needed, but you can do this if you want to

    class DivingWeasel : ImageRenderObject

    {

        public DivingWeasel(IDeviceContext context) : base(context) 

        {

            this.ImageFile = "DivingWeasel.png";

        }

    }

​

    //Not really needed, but you can do this if you want to

    class BarkingHorse : TexturedRenderObject

    {

        public BarkingHorse(IDeviceContext context) : base(context)

        {

            Children.Add(new CullingBird(context));

            Children.Add(new DivingWeasel(context));

        }

    }

​

​

    class Almighty 

    {

        public void Render(RenderObject obj)

        {

            obj.Render();

        }

    }

​

    class RenderObjectFactory

    {

        protected readonly IDeviceContext _context;

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        public RenderObjectFactory(IDeviceContext context)

        {

            _context = context;

        }

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        public T Create<T>(string name) where T : RenderObject

        {

            return Create<T>(name, Enumerable.Empty<RenderObject>());

        }

​

        public T Create<T>(string name, string imageFile) where T : ImageRenderObject

        {

            var instance = Create<T>(name, Enumerable.Empty<RenderObject>());

            instance.ImageFile = imageFile;

            return instance;

        }

​

        public T Create<T>(string name, IEnumerable<RenderObject> children) where T : RenderObject

        {

            var type = typeof(T);

            var instance = (T)Activator.CreateInstance(type, new[] {_context} );

            instance.Children.AddRange(children);

            instance.Name = name;

            return instance;

        }

    }

​

    public class Program

    {

​

        public static void Main()

        {

            var factory = new RenderObjectFactory(new DeviceContext());

            var divingWeasel = factory.Create<ImageRenderObject>("DivingWeasel", "DivingWeasel.png");

            var cullingBird = factory.Create<ImageRenderObject>("CullingBird", "CullingBird.png");

            var barkingHorse = factory.Create<TexturedRenderObject>("BarkingHorse", new RenderObject[] {divingWeasel, cullingBird} );

            var almighty = new Almighty();

            almighty.Render(barkingHorse);

        }

    }

}

​